Several methods are currently used to recover polymer resins from solution. Some of the methods are energy intensive and require large quantities of steam to accomplish removal of the solvent. Other methods require high viscosity process equipment which require a high investment cost. Further, the residual solvent contained in the product powder or particles is difficult to remove.
U.S. Pat. No. 456,172 discloses the production of polycarbonate resin particles having high bulk density that are produced by a process in which a polymer solution or polymer solution and water mixture are fed into an agitation tank filled into a water bath having a temperature higher than the boiling point of methylene chloride. The polycarbonate is recovered in the form of an aqueous slurry.
This process has the disadvantage that the polycarbonate often agglomerates, producing a large sticky mass prior to precipitation, leading to difficulties in processing. In this process, an off-tank wet pulverizer was used to ground the large sticky mass. In some cases, non-solvents are used to overcome this problem. The utilization of high viscosity process equipment is another solution to the problem of agglomeration.
It would be desirable to develop a process for the recovery of polymers in solution which avoids the use of high shear agitation in the tank, large quantities of anti-solvent and/or water, large expeditures of energy, and special equipment.